1. Field of the Invention
The present invention relates to a control apparatus for a robot, and in particular in an industrial robot, to a method of outputting a stop signal for the periphery of the robot and to the configuration of a safety circuit for generating the stop signal when the robot is stopped in case of abnormality in the periphery of the robot.
2. Description of the Related Art
An industrial robot is provided with emergency stop switches in order to secure the safety of both the operator of the robot and the workers in the periphery of the robot. Since these emergency stop switches are electrically connected to a safety circuit in series, the operation of any emergency stop switch causes the switching OFF of a servo power supply for driving a motor in the robot body.
These emergency stop switches indicate those switches for detecting the occurrence of a factor harmful to the safety, and include: an emergency stop switch provided in the body of the control apparatus; a door open-close switch provided in a safety fence for insuring a safety region in the periphery of the robot; an external emergency stop switch in a peripheral system; and an over travel switch for the robot body. Each switch is configured in linkage with the driving circuit of the servo power supply so as to control the switching ON permission and the switching OFF of the servo power supply. A prior art safety apparatus for an industrial robot is described below with reference to FIG. 8.
In a safety circuit of a robot body 1 shown in FIG. 8, disposed in series are switches 21 to 2n each corresponding to a factor inhibiting the switching ON of a servo power supply 4 to the robot body 1. One end of the switch 21 is supplied with a 24 V voltage, while the last end of the switch 2n is provided with a relay 3 for controlling the switching ON and switching OFF of the servo power supply, whereby a first signal line is formed. Further, a signal of servo switching ON permission is provided from a control apparatus 5 to the servo power supply 4. Without a factor inhibiting the switching ON of the servo power supply to the robot body 1, each switch 21 to 2n is closed thereby to provide the 24 V voltage on the first signal line. A relay coil 31 is then excited thereby to close a relay contact 32. Then, finally, a servo power supply switching ON circuit in the servo power supply 4 is driven. When switched ON, the servo power supply starts to energize (control) a motor 11 included in the robot body 1, while a lock (brake 12) circuit of a shaft of the motor 11 is switched OFF.
In this state, when at least one of the switches 21 to 2n is operated (to become open) due to occurrence of a factor inhibiting the switching ON of the servo power supply, the first signal line is switched OFF, and the 24 V voltage is not supplied. At that time, by monitoring the potential in the end point on the relay 3 side of each switch with a control apparatus 5, it is known which switch is open. Further, the relay coil 31 becomes unexcited thereby to open the relay contact 32. The servo power supply is then switched OFF thereby to stop to energize (control) the motor 11 in the robot body 1, while the brake 12 of the shaft of the motor 11 is switched ON.
As such, as is described in Japanese Laid-Open Patent Publication No. Hei 10-217180, when any of the switches 21 to 2n becomes open, the first signal line which is the servo power supply switching ON permission line is switched OFF, whereby the servo power supply is switched OFF thereby to cause immediate stop of the robot.
In the prior art safety apparatus for an industrial robot as described above, a signal for sending the emergency stop to external devices is output by the open-close of the relay contact 32. Further, in a production line in which each of a plurality of robots is disposed in each work area, the emergency stop of each work area is monitored using the above-mentioned signal. Accordingly, even when a trouble occurs only in some of the work areas, the robots in all of the areas are immediately stopped. Therefore, even when a work area is to be stopped to ensure the safety in the work area in case of a trouble (such as a change of expendable parts) which concerns the work area alone and does not affect the other work areas, the whole line is stopped in accordance with the prior art configuration. This causes the problem of reducing the work efficiency.
Further, since the switching OFF of the servo power supply for the industrial robot is carried out by breaking the switch contact of a limit switch and the like of each switch 21 to 2n, in case of occurrence of a contact fusion in any switch, the servo power supply is not properly switched OFF even in case of occurrence of the emergency stop factor corresponding to the switch. Furthermore, the control apparatus 5 can not detect the occurrence position of the fusion, and hence the reliability of the safety circuit of the control apparatus 5 is not secured.
An object of the present invention is to provide a control apparatus for a robot in which the work efficiency is improved in the whole robot peripheral system including the robot, and in which considering the increase in the consciousness of safety such as the standardization of safety apparatuses, both the reliability of the safety circuit of the control apparatus for a robot and the ensuring of the safety are improved.
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the switch circuit, and wherein each of the plurality of switches is provided with an intermediate output signal line for extracting the operation signal, or the emergency stop signal thereof.
In accordance with the control apparatus for a robot in accordance with the present invention, by connecting the intermediate output signal lines to peripheral devices outside the robot, a factor to cause the stop of the robot body alone can be distinguished from a factor to cause the stop of both the robot body and the peripheral devices. This permits the safety circuit of the whole robot system to be configured with flexibility, and accordingly the work efficiency can be improved without degrading the safety.
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the switch circuit, wherein each of the plurality of switches comprises a first open-close contact and a second open-close contact both operating simultaneously, wherein every first open-close contact of each of the plurality of the switches is interconnected in series by a first signal line, while every second open-close contact of each of the plurality of the switches is interconnected in series by a second signal line, and wherein an intermediate output signal line for extracting the operation signal or the emergency stop signal of each of the plurality of switches is connected to at least one of the first signal line and the second signal line.
In accordance with the control apparatus for a robot in accordance with the present invention, a case to stop the whole system including the robot body, a case to cause the stop of the robot body and a part of peripheral devices, and a case to cause the stop of the robot body alone can be distinguished with each other. This permits the safety circuit of the whole robot system to be configured with flexibility, and accordingly the work efficiency can be improved without degrading the safety.
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the switch circuit, wherein each of the plurality of switches comprises a first open-close contact and a second open-close contact both operating simultaneously, wherein every first open-close contact of each of the plurality of the switches is interconnected in series by a first signal line, while every second open-close contact of each of the plurality of the switches is interconnected in series by a second signal line, wherein each of the first signal line and the second signal line is provided with a voltage of an opposite polarity with each other relatively to the plurality of switches, and wherein a relay for extracting the operation signal or the emergency stop signal of the plurality of switches is connected to the end on the same side of each of the first signal line and the second signal line.
In accordance with the control apparatus for a robot in accordance with the present invention, in case of occurrence of a short circuit between the first signal line and the second signal line for controlling the switching ON and OFF of the servo power supply for driving the motor, the servo power supply can be immediately switched OFF. This improves the safety of the control apparatus for a robot.
A control apparatus for a robot in accordance with the above-mentioned present invention further comprises current interrupting means disposed in the end opposite to the relays in the first signal line and the second signal line and for interrupting a current greater than or equal to a predetermined value.
In accordance with the control apparatus for a robot in accordance with the present invention, in case of occurrence of a short circuit between the first signal line and the second signal line, the servo power supply can be immediately switched OFF, while the occurrence of the short circuit can be detected by the control apparatus. As such, since the control apparatus can detect the occurrence of abnormality and the occurrence position of abnormality in the signal lines, the repair work of the control apparatus is speeded up.
In a control apparatus for a robot in accordance with the above-mentioned present invention, a fuse is used as the current interrupting means.
Further, in a control apparatus for a robot in accordance with the present invention, the plurality of switches are disposed in the order of priority.
In accordance with the control apparatus for a robot in accordance with the present invention, the disposing of the plurality of switches in the order of priority permits the optimal setting depending on the system to be used, for example, when a case to stop the whole system including the robot body, a case to cause the stop of the robot body and a part of peripheral devices, and a case to cause the stop of the robot body alone are to be distinguished with each other.
In a control apparatus for a robot in accordance with the above-mentioned present invention, an intermediate output signal line for extracting the operation signal or the emergency stop signal of each of the plurality of switches is connected to at least one of the first signal line and the second signal line.
In accordance with the control apparatus for a robot in accordance with the present invention, the disposing of the plurality of switches in the order of priority permits the optimal setting depending on the system to be used when a case to stop the whole system including the robot body, a case to cause the stop of the robot body and a part of peripheral devices, and a case to cause the stop of the robot body alone are to be distinguished with each other. Further, in case of occurrence of a short circuit between the first signal line and the second signal line, the servo power supply can be immediately switched OFF, while the occurrence of the short circuit can be detected by the control apparatus.